Method and apparatus for refrigerating railroad cars



K. V. PLUMMER ET AL METHOD AND APPARATUS FOR REFRIGERATING .March 2l, 1950 RAILROAD CARS 2 Sheets-Sheet 1 Filed April 19, 1948 QN Q March 2, 31.950 K. v. PLUMMER s-:TAL 2,5014l METHOD AND APPARATUS FoR REFRIGERATING v RAILROAD CARS Filed April 1.9, 1948 2 Sheets-Sheet 2 L32) L1 KM fil-5.3

47 I 5g 5 .55 .52 I A 53 50 58 l INVENToRs., KEA/NEM PLUMA/fe @055er 0. P//re Patented Mar. 21, 1950 METHOD AND APPARATUS FOR REFRIG- ERATIN G RAILROAD CARS Kenneth V. Plummer, San Francisco, Calif., and

Robert D. Pike, Greenwich, Conn.; said Plummer assigner to said Pike Application April 19, 1948, Serial No. 21,976

14 Claims.

Ourv present invention is concerned with a railroad car and method for its refrigeration, particularly for the purpose of maintaining temperatures suitable for the shipment of frozen foods.

An object of the invention is to provide a method and apparatus for refrigerating a railroad car in which it is feasible to ship frozen foods across the continent in the hottest summer weather from points of origin on the Pacific Coast to the Atlantic seaboard points of destination with no more than one reicing en route, while holding the maximum temperature in the car uniformly at about F. or a little below.

An object of the invention is to provide a method of refrigerating a railroad car by the sublimation of solid carbon dioxide, referred to hereinafter as Dry Ice and the melting of water ice mixed with salt, or other melting point depressant, so that the maximum temperature in the car is controlled according to the melting temperature of the salted water ice.

Another object of our invention is to provide a refrigerating system for a railroad car with a forced draft of air as the heat exchange medium, with a controlled or predetermined part of the air draft being passed, in the course of its circulation, into contact with a heat transfer surface cooled by a low temperature overhead refrigerant, and with all of the air draft, during its circulation cycle, being brought into heat exchange relation with salted water ice.

A still further object of the invention is to provide a refrigerated railroad car having overhead bunkers for Dry Ice and end bunkers for water ice, and having an air circulating system in which air from the goods storage space is mixed with air chilled by heat exchange relation with Dry Ice and the mixed air is passedinto contact with salted water ice and then part being discharged over the goods in the storage space and a controllable portion of the remainder being diverted from the storage space into heat exchange relation with Dry Ice from whence the latter air flows to mix with theexhaust air from the storage space to complete the circuit.

Other objects and advantages of the invention will be apparent from the following description of a preferred form of the invention, reference being made to the accompanying drawings wherein:

Fig. 1 is a longitudinal sectional view of' a reon line l--I of Fig. 3;

Fig. 2 is a fragmentary plan view of the top of the refrigerated railroad car;

Fig. 3 is a view in section taken substantially on line 3--3 of Fig. 1, but on a larger scale;

Fig. 4 is a fragmentary view in section taken on line 4--4 of Fig. 1 but on'a larger scale; and,

Fig. 5 is a fragmentary View showing certain structure shown in Fig. 4 but on a larger scale.

We are well aware that cars with end bunkers lled with coarse water ice and about 30% of its weight of salt, with fans motivated by the turning of the axles when the car is running, whereby aA current of air is forced up through and around the ice in the bunkers, out over the goods, down through the goods to the limited extent usually permitted because of the tight stacking of the packages and through side wall nues, all of the circulating air eventually passing under the oor racks and back to the fan, thus imparting a uniform temperature to the goods, are well known. However, such cars, while imparting quite uniform temperatures to the goods, cannot be depended upon to hold a temperature much, if any, below 15 F. Also, cars of this type must be reiced every 24 hours, while being hauled across the continent under even the mildest summer conditions.

We arel also aware that cars with overhead bunkers or tanks distributed along the roof and adapted t0 be fed with water ice and salt or with Dry Ice through overhead hatches, are well known. Cars of this type hitherto in use depend upon natural air circulation to distribute the refrigerating effect and such natural air circulation is in fact greater in this type of car than in the end bunker cars, because of the high position in the car of the cold surfaces. However, the temperatures in this type of car cannot be controlled so that there is more refrigeration than is required which results in ineflicient use of the refrigerant, and the temperatures are not uniform throughout the goods.

We have improved on the mentioned existing railroad car refrigerating systems by providing Dry Ice bunkers in the top of the car over the goods storage space but having flues for diverting a forced draft of air contacting the heat conducting surfaces of these bunkers thence around the sides of the storage compartment through side wall ues to a mixing chamber beneath the storage space where this chilled air is mixed with air exhausting from the storage space. However, if the goods are tightly packed for reasons of economy,y very little air passes 5 through thegoods inthe storage space, the preponderant part of the circulating stream drawing through the side wall nues. This mixture of chilled and` exhausted air is then forced over salted water ice in end bunkers in the car where the air is chilled substantially to the temperature of the melting point of the water ice, which temperature may be lowered to approximately F. by the proper amount of salt. The air owiug over the water ice is then directed into the upper part of the goods storage space where part thereof flows down through the goods and is exhausted into the mixing chamber below the floor of the storage space and the remainder of the air not passing through the goods is directed into flues for passage to the mixing chamber` by way of the side wall flues and a controllable portion of this air is adapted to be passed into heat exchange relation with the Dry Ice in the top bunkers. The amount of refrigeration furnished by the Dry Ice is maintained below the normal summer time total refrigeration requirement so that there will be melting of the water ice at all times which automatically maintains a substantially constant maximum temperature in the storage space. The amount of refrigeration furnished byv the Dry Ice may be controlled to a certain extent by con trolling the openings in passages which b i/pass the circulating air from the Dry Ice bunkers to the side wall flues, however this control need not be exercised by use of dampers, but may be effected merely by the proper choice of the size oi the openings in building the car. When atmospheric temperatures of say 50 F. or lower exist, the temperature in the storage space may fall below 0 F., but this will not be detrimental to frozen goods.

We have provided a refrigerated railroad car which will hold the necessary maximum temperature throughout summer temperatures and at the same time the refrigerant is utilized with a` maximum of eiiciency so that reicing of the car may be relatively infrequent.

Referring now to the drawings, we have shown one form of our invention embodied in a railroad car ID which is adapted to transport goods such as frozen foods, which must be maintained at a temperature of not over 0 F., for example. It will be understood that the structural features of the car, other than the refrigerating system, ard form. The car comprises top, side, end and bottom walls II, I2, I3 and I4, respectively, which are insulated in the usual manner. Water ice bunkers IS and I1 are formed at opposite ends of the car by bulkheads I9 and 20, respectively, which bulkheads extend transversely of the car are not shown in detail as they may be of standand terminate short of the top and bottom to provide air openings 2| and 22. Preferably, louvers 24 are provided in the upper openings to direct air laterally toward the center of the car. Each bunker is provided with racks 25 for supporting coarse water ice in the bunker while permitting air to flow upwardly through between the pieces of ice. Coarse ice consists of pieces of ice in the order of up to to 12" in diameter, which form a bed having interstices which provide numerous air passages through the bed, giving a large area for transfer of heat from the air to the ice to allow for the transfer of the latent heat of melting. It will be noted that the racks are positioned somewhat above the bottom of the car to permit free ow of air thereunder. We also prefer to provide metal screening 26 to protect the bunker walls and to prevent ice from inadvertently entering the louvres 24. Suitable drains,

not shown, should be provided for carrying off the water from the melted ice. Ice and salt are loaded into the bunkers by hatches 21 formed in the top of the car.

The space in the car intermediate the bulkheads constitutes the goods storage space, except for the overhead bunkers which are described hereinafter, and the usual loading doorways 28, are provided in the sides. The oor of the storage space is indicated at 20 and this iioor is elevated above the bottom of the car about 6 inches to provide an air mixing chamber 39. The iioor 29 may be formed of floor racks comprised of six to eight inch wide planks moimted on suitable supports 32 and spaced apart an inch or so to enable air to pass downwardly through the floor. The floor racks extend to the openings 2I in the bunkers and the side edges thereof are spaced from the sides of the car to form air passageways into the mixing chamber 30, the purpose of which will be explained more fully hereinafter.

A series of Dry Ice bunkers 35 are disposed at spaced intervals along the top of the car intermediate the water ice bunkers, and each Dry Ice bunker is comprised of an open top sheet metal container structure 36 which is secured to the top of the car with the opening in alignment with a pair of hatches 37. The container structures each extend substantially transversely of the car and they are supported by angle irons 38 which are held at opposite ends by brackets 38. Air passages 39 and 40 are formed beneath the containers 36 extending from the central part of the car laterally to the sides thereof. These passages are formed by sloping ceiling panels 42 and 43, respectively, and divider members 44, which members extend from the ceiling panels to the bottom edges of the containers 38 and project from the inner edges of the ceiling panels toward the sides of the car but terminate short thereof. At each end of the car extensions 46 on the ceiling members curve upwardly and project over the louvers 24 to deflect air entering the storage space between the louvres downwardly. A shallow, inverted V shape trough 4l is disposed immediately beneath the bunkers 35 and extends substantially lengthwise of the gap formed between the inner edges of the ceiling panels 42 and 43 and it serves to deect air laterally over the ceiling panels. The member 47 and inner edges of the ceiling panels cooperate to form a longitudinal air passage 5D at the top of the food storage compartment. It will be seen in Fig. 3

f that air owing through passages 30 and 49 will come into close contact with the heat conducting bottom wall of the Dry Ice bunkers and will become considerably chilled thereby. The sloping ceiling panels will cause the air to naturally gravitate to the sides of the car, the purpose of which will be brought out presently. Also, any moisture condensing and then melting will drain toward the side ues due to the slope of the ceiling panels, thereby keeping it away from the goods.

The Dry Ice bunkers are spaced apart to provide air passages 52 leading from the central passage to thel sides of the car. These passages are formed by the ceiling panels 42, 53, partition members 44 and plate 53 which are attached to vertical partitions 56 and the entrances to these passages may be controlled by dampers 55 pivotally mounted in journals in the partitions 44. These dampers may be operated by any suitable means to regulate the ow of air through these passages. The greater volumev of air flowing through these passages: correspondingly decreases the volume flowing in contact with the Dry Ice container bottom plates, thereby reducing the rate of sublimationof the Dry Ice.. The dampers 55'may, however, be omitted. and the desired now of air be obtained, or controlled, by the proper choice of size of the openings when building the car. The' partitions 56 are preferablyr spaced a short distance from. the side walls of containers 36, respectively, of the Dry Ice bunkers andi the space so formed is preferably closed at the bottom: so that air admitted through the openings into 52. may not come intov direct contact with Dry Ice cooled surfaces. In further pursuit of this end, the space 5d may be llecl with any suit ablev heat insulating material.

The Vlaterally extending air passages 30, 40 and 52 connect with side iiues 5l which arey formed by the side walls of the car and partitions 58, which may be formedv of plywood secured to suitable studding, not shown, and spaced from the side walls. The lower ends of the flues connect with the mixing chamber 30 beneath the oor 20.

Fans 60 are located at the ends ofr the mixing chamber 30 for forcing air toward the ends of the caras indicated by the arrows in Fig. l. The fans are preferably driven by rotation of the' axles of the car by belting, not shown. The operation of the fans withdraws air from the goods storage space into the chamber 30 through the openings in the floor 29 and through the passages 39, 40 and 52 (the latter only if opened by damper 55) and side flues 5l. From the mixing chamber 30 the air is directed upwardly through the water ice bunkers and back into the storage space through louvers 24E. Thus, all of the air entering the storage space issues directly from the water ice bunkers. When the refrigerating system4 is in operation to maintain a maximum of'0 F., the

bunkers I6 and il are lled with coarse chunks of water ice preferably with 30 salt, and the bunkers 35 are nlled with Dfry Ice, preferably in pulu verized form. Air exhausted from the storage space is inter" 'ixed in chamber 30 with air chilled by the Dry Ice and passing downwardly through flues 5l. The mixed air has a temperature which will be somewhat above 0 F. due to'inltra-tion oi heat into the circulation through the side walls, iloor and roof of the car, as well as from the goods, and this air then passes upwardly through the water ice which is at least in part at 6 F., the melting point of water ice and 30% salt. Thus, air entering the storage space will be* at about 00 Since the volume of air contacting the Dry Ice bunker walls is, under average sumf mer conditions, insufficient to refrigerate the car at 0 the water ice will melt to some extent under such conditions, and this melting will cause a uniform. maximum temperature of about 0 F'. to prevail in the goods. This automatic main Atenance of a maximum temperature of about 0J is due to the fact that if the temperature of the-air entering the ice bunkers is about 0 to 5 F., but above 6 F., the theoretical melting point of ice with 30% salt, meltage of ice will occur only in the areas where the ice and salt are in contact, forming the correct mixture, thereby reducing the air temperature to approximately the temperature at which water ice and salt melt. The rate of meltage will correspond to the elevation of the air temperature above about 6 F. When the air temperature is below the melting point of the ice and salt mixture, no melting takesplace and the -ice will be merely further chilled by the air. But, as we have stated here# nbefora refrigeration furnished' by the 'Dry' Ice is insuiiicient, under ordinary conditions, to fur"- nish all ofthe required refrigeration to hold the load at 0 F. or a little below, and consequently the'water ice will be constantly melting at the rate to provide themargin of refrigeration neces sary to chill the air to about 0 F. Invthe event itfis desired to increase the refrigerating eifect of the. Dry Ice, such as in extremely warm weather, the damper 55-may all be closed and'this increases the flow of air in contact with the Dry Ice bunkers. Frost may form on the exposed bottom plates of the Dry Ice bunkers and this will reduce the rate of heat exchange between theair andi the Dry Ice, to that extent being equivalent to opening dampers 55. In cooler weather'dampers 55 are preferably opened and airwhich would otherwise traverse the chilling passages 3.0 and 40 will be bypassed to some extent through vthe passage 521 soy thatv the entering the water ice bunkers will not'beas celdas otherwise.

The Dry Ice bunkers may be vented to the atmosphere or they'may discharge the sublinied gas into the storagechamber, if desired. Ordinarily, we prefer, however, to allow the gas toescape inside'the car, thus utilizing in f-ull the refrigerating value of the Dry Ice.

When the car is stationary the fans will be inoperative, but by reason of the Dry Ice bunkers being disposed overhead the natural iiow of the air byconvection will be similar to thatV caused by operation of the fans though far less in amount so that the temperature in the storage space will not be materially altered unless the shutdown of the fans is unduly prolonged. Ordinarily, the refrigerator car will only to stationary for a matter of an hour or so at one time so that there will be no deleterious rise in temperature, or departure vfrom its uniformity throughout the goods.

In practice, the loads of frozen foods originate at a number of points, for example, over the entire State of California, and the cars after loading, pass on to a limited number of gateways where the trains are made up, as for example, Colton and Roseville, California. As an example of the handling of a car by our method, shortly beforeV loading, we may place about 12,00016,000 lbs. course water ice and 3,600-4,800 lbs. salt in the end bunkers. This will pre-cool the car before loading the goods. After loading the goods, the car is hauled to the nearest gateway point and is there reiced with approximately 200G-4,000 lbs. water ice and its accompanying 30% salt, thus lling the end bunkers. The Dry Ice plants will be preferably located `at these same gateway points. -We usually prefer to provide suicient overhead bunker space to load about 6,900 lbs. Dryy Ice in pulverized form, weighing about '72 lbs. per c. f. This load will last about 268 hours for complete sublimation, which is more than enough for the car to reach Chicago, which would ordinarily take about seven days, or 168 hours. As about 7,400 lbs of Dry Ice will ordinarily be sublimed in ourl car in hauling frozen foods to thev East Coast, we ordinarily prefer to add about 1,000 lbs. at Chicago. It will be understood that this relatively heavy consumption of Dry Ice is due to the delays often encounted in unloading on the East Coast At Chicago we also ordinarily prefer' toi-lll the end bunkers with water ice and salt. The meltage of water ice en route to Chicago is ordinarily about 10,000 lbs., andy this would bring the water ice in the end bunkers too low-to be safe, were it not for the presence of the Dry Ice. But so long as a surplus of' Dry Ice remains in the overhead bunkers, the car is safe, and if the stated amount of Dry Ice be added at Chicago, it will ordinarily be sufficient to have the water ice bunkers as little as 1/2 full on leaving Chicago. This eiects a considerable economy because the water ice and salt in ordinary practice are carried in full load right through to the unloading point and the ice and salt left after unloading are completely wasted. By the use of our invention, however, so long as we carry sufficient Dry Ice, We reduce the end loss of water ice and salt to about 1/3 that which is experienced by the present method.

Although we have described but one form of the invention other forms may be adopted, all falling Within the scope of the claims which follow.

We claim:

1. The method of refrigerating a railroad car which comprises, withdrawing air from the upper portion of the storage space of the car, chilling a predetermined portion of the air as it is withdrawn by a low temperature refrigerant, mixing said chilled air with the balance of the nonchilled air withdrawn from the storage space, passing the mixed air in intimate heat exchange relation with water ice, and circulating the mixed air to the storage space of the car.

2. The method of refrigerating a railroad car which comprises, withdrawing air from the lower and upper portions of the storage space of the car, chilling a controlled portion of the air from the upper portion by a refrigerant, mixing said air from the lower portion of the storage space with said chilled air and the remainder of the air from the upper portion of the storage space, passing the mixed air in intimate heat exchange relation with water ice, and then passing the air directly into the storage space of the car.

3. A refrigerated railroad car comprising, a storage space; an air mixing chamber beneath the storage space and communicating with the latter whereby air may be drawn from the storage space into said chamber; a Dry Ice bunker at the top of the car; means forming a plurality of air passages leading from the upper part of the storage space and downwardly to said mixing chamber, at least one of said passages being in heat exchange relation with a wall of the said bunk-er; a water ice bunker adjacent to the storage space, said water ice bunker being connected by air passageways with said mixing chamber and said storage space; air impelling means for circulating air from the mixing chamber through the water ice bunker and into the storage space; and means for regulating the flow of air through at least one of said air passages.

4. A refrigerated railroad car comprising, a storage space; an air mixing chamber beneath the storage space and communicating with the latter whereby air may be drawn from the storage space into said chamber; a Dry Ice bunker at the top of the car; means forming a plurality of air passages leading from the upper part of the storage space and downwardly to said mixing chamber, at least one of said passages being in close heat exchange relation with a wall of the said bunker; damper means for regulating the ow of air through the other of said passages; a water ice bunker adjacent to the storage space, said water ice bunker being connected by air ypassageways with said mixing chamber and said storage space; and air impellng means for circulating air from the mixing chamber through the water ice bunker and into the storage space.

5. A refrigerated railroad car comprising, a

storage space; an air mixing chamber beneath the storage space and communicating with the latter whereby air may be drawn from the storage space into said chamber, a plurality of Dry Ice bunkers at the top of the car, said bunkers being spaced from one another longitudinally of the car; means forming air passages extending laterally with respect to the longitudinal axis of the car and leading from the upper part of the storage space to the side of the car, certain of said -passages being in heat exchange relation with the bottom walls of the bunkers respectively and certain other of said passages being disposed intermediate adjacent spaced bunkers; iiues at the side of the car connecting the ends of said passages at the side of the car and leading downwardly into said mixing chamber; a water ice bunker adjacent to the storage space, said water ice bunkers being connected at the bottom thereof by an air passageway with said mixing chamber and connected at the top thereof with the top of said storage space; and air impelling means for circulating air from the mixing chamber upwardly through the water ice bunker and into the storage space.

6. A refrigerated railroad car comprising, a storage space; an air mixing chamber beneath the storage space and communicating with the latter whereby air may be drawn from the storage space into said chamber; a plurality of Dry Ice bunkers at the top of the car, each bunker extending transversely of the car and spaced apart longitudinally of the car; ceiling panels extending beneath said bunkers from the centra-l portion of the car laterally toward the sides of the car and spaced from the bottoms of said bunkers, the inner longitudinal edges of said panels being spaced apart to provide an air inlet to the space above the panels; partitions extendu ing laterally of the longitudinal axis of the cai and cooperating with the ceiling panels to form air passages in direct contact with a wall of the respective bunkers and to form passages intermediate said bunkers parallel with the first mentioned passages; partition members spaced from the side walls of the cars and extending vertically to form flues connecting the ends of said air passages and leading downwardly into said mixing chambers; dampers for regulating the flow of air through certain of said air passages; water ice bunkers at opposite ends of said storage space, said water ice bunkers being connected at the bottoms thereof by air passageways with said mixing chamber and connected at the upper portions thereof by air passages with the upper portion of said storage space; and air impelling means for circulating air from the mixing chamber upwardly through the water ice bunker and into the storage space.

'7. A refrigerated railroad car comprising, a storage space; an air mixing chamber beneath the storage space and communicating with the latter whereby air may be drawn from the storage space into said chamber; a plurality of Dry Ice bunkers at the top of the car, each bunker extending transversely of the car and spaced apart longitudinally of the car; ceiling panels extending beneath said bunkers from the central portion of the car laterally toward the sides of the car and spaced from the bottoms of said bunkers, the inner longitudinal edges of said panels being spaced apart to provide an air inlet to the space above the panels; partitions extending laterally of the longitudinal axis of the car and cooperating with the ceiling panels to form air passages Ain direct "contact'with a wall'of the bunkers; water ice bunkers at opposite ends ofsaid storage space, said water 'ice bunkers being connected at the bottoms thereof vby-air passageways with said mixing chamber and'connected at the upper portions `thereof by air passages `with the upper portion of vsaid storage space; and air impelling :means for circula-ting air from the mixing Achamber upwardly l'through `the water 'ice bunker and iintovthe storage space.

v8. 'The method `of exercising inherent 4automatic control of temperature in a refrigerator car and providing temperature of about F. throughout the goods, which consists in Ifofrcing4 a circulation of air within the car, at least a portion of the said air traversing Dry Ice cooled surfaces in the upper part ,of the car, navinginsuflicient cooling Aeffect to supply all of the required refrigeration, thence passing along the bottom of the car underneath the oor racks through fans and upwardlly through the end bunkers supplied with a mixture of water 4ice and melting point depressant, whereby meltage of the water ice provides the refrigeration not supplied by the Dry Ice, passing the air from the tops of the end bunkers over the top of the goods and passing a part of the air which does not pass downwardly through the goods, into contact with the said Dry Ice cooled surfaces and thence downwardly through side flues, and diverting a controllable part of the air out of contact with the Dry Ice cooled surfaces directly to the said side flues, mixing all of the air beneath the floor racks and returning the total stream in recirculation through the fans.

9. The method of exercising inherent automatic control of temperature in a refrigerator car and providing substantially uniform maximum temperature of about 0o F. throughout the goods, which consists in forcing a circulation of air upwardly through the end bunkers in contact with water ice and melting point depressant, furnishing a part of the refrigeration required and cooling the air to a maximum temperature of about 0 passing the air into the car over the goods from the tops of the end bunkers, a part passing downwardly through the goods, a part passing into ducts in the ceiling of the car, the upper surfaces of which are the bottom conducting plates of bunkers containing Dry Ice, situated under the roof of the car and furnishing the balance of refrigeration, thence diverted downwardly into side nues, and other controllable part, or the balance of the flow, being diverted out of contact with the Dry Ice cooled surfaces, the entire flow passing beneath the floor racks and thereafter being re-circulatedl0. A refrigerated railroad car comprising, a storage space, an air chamber beneath the storage space, a plurality of bunkers containing a low temperature refrigerant at the top of the car, said bunkers being spaced from one another longitudinally of the car, means forming air passages extending laterally with respect to the longitudinal axis of the car and connecting the upper part of the storage space to the side of a substantially 'uniform vmaximumI the car, Kcertain of said passages being vin heat exchange relation with the walls of said `bunkers andcerta'in otherof-said passages being disposed immediately fadjacent thereto, iues at the side of the car interconnecting the vends of said "pas-V sages with said airchamber, a refrigerating come partment adjacent to kthe storage space, saidv compartment being connected lat the bottom thereof 2Vby an vair passageway Ato said air chambe, rand connected to the y'top thereof with .the topfof said-storagerspace, vandai-r `impelling means disposed in saidialir :chamber for forcing a cirey culation `of vair 'throughoutfthe car into heat ex-` change 'relation with fthe refrigerants and to .the storage space.

ill. 'A lrrefrigerated yrailroad car comprising, a.

storage space; an vair chamberbeneath the storl from lthe central portion lof 'the car laterally towardfthe sides of 'thecar and-spaced from-the bottoms of said bunkers, the inner longitudinal edges of said panels being spaced -apart to provide an air lpassage 'to thespace abo-ve the pan-v els; partitions `vextending laterally of the 'longitudinal axis of the-car and 'cooperating with the ceiling y'panels to form air'passages infdirectcontact with a wall of the respective bunkers and tofiform passages intermediate said bunkers parallel with the first mentioned passages; partition members spaced from the side walls of the car and extending vertically to form flues connecting the ends of said air passages with said chamber; water ice bunkers at opposite ends of said storage space, said water ice bunkers being connected at the bottoms thereof by air passageways with said air chamber and connected at the upper portions thereof by air passages with the upper portion of said storage space; and air impelling means for forcing air through the air chamber, through the water ice bunkers, through the storage space, and through the air pas* sages.

12. The method of maintaining substantially at a predetermined temperature the storage space compartment of a refrigerator car having the compartment spaced from the inner surfaces of the car, having air passageways between and interconnecting the compartment and car, and having refrigerants disposed in the ends and ceiling of the car adjacent the storage space, which comprises: drawing air transversely in symmetrical vpatterns about the periphery of the storage space, a portion o f said air contacting the ceiling refrigerant in heat exchange relation: withdrawing said peripherally circulated air to each end of the car in divergent streams; passing the longitudinally directed air streams in heat exchange relationship the refrigerants at opposite ends of the car in symmetrical patterns; and recirculating the refrigerated air in the manner above defined, whereby the circulating air dissipates to the refrigera-nts heat conducted into the car, and whereby the storage compartment is shielded from the effect of outside heat by the circulating air and maintained at a predetermined refrigerating temperature.

13. The method of maintaining substantially at a uniform maximum temperature of about 0" F. the storage space compartment of a refrigerator car having the compartment spaced from the inner surfaces of the car, having air passageways between and interconnecting the compartment and car, and having bunkers containing Dry Ice disposed in the ceiling of the car and bunkers containing ice and a melting point depressant located adjacent the storage space at the ends of the car, which comprises: drawing air transversely in symmetrical patterns about the periphery of the storage space, a predetermined portion of said air contacting the Dry Ice bunkers in heat exchange relation, whereby part of the required refrigeration is provided; withdrawing said peripherally circulated air to each end of the car in divergent streams; passing the longitudinally directed air streams through the water ice refrigerants in symmetrical patterns at opposite ends of the car, whereby meltage of the water ice provides the balance of the total refrigeration required; and recirculating the refrigerated air in the manner above dened, whereby the circulating air continuously transfers to the refrigerants heat conducted into the car, and whereby the storage compartment is substantially shielded from heat from the outside by the circulating air and maintained at a .predetermined refrigerating temperature.

14. The method of exercising inherent automatic control of temperature in a refrigerator car having a refrigerant mixture of water ice and melting point depressant in vertically extending bunkers disposed at the ends of the car, o

a storage space extending therebetween, said storage space being spaced from the car oor by a slotted rack, a second low temperature refrig erant disposed in laterally extending bunkers in the ceiling of the car, peripheral air passageways in the ceiling and sides of the car about the storage space interconnecting the upper part of the storage space and the car oor therebeneath and providing heat exchange access therein with the overhead refrigerant, and air passages interconnecting the end bunkers, upper storage space, and car oor beneath the storage space, which comprises: drawing air transversely about the periphery of the storage space through said peripherally interconnected air passageways, a portion of said air contacting the ceiling refrigerant in heat exchange relation, withdrawing peripherally circulated air to each end of the car in divergent streams, cycling said air streams through refrigerants disposed at the ends of the car convergently back along the longitudinal axis of the car, and recirculating the refrigerated air in the method above dened.

KENNETH V. PLUNLMER. ROBERT D. PIKE.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,256,197 Finger Sept. 16, 1941 2.324.749 Wieden July 20, 1943 

